To mix in the medium, a syringe cannula (hollow needle) has been used to pass through a perforable seal or plug of the receptacle, such as an infusion container. Then, the medium is injected into the receptacle by expression of the syringe. This procedure requires the preliminary operational step of filling the syringe, the syringe being filled with the desired amount of the medium from a reservoir or the syringe being filled from a conventional vial holding the measured amount of the medium in question. These decanting steps are time-consuming, in that cannula and syringe must be removed from their packaging, the cannula mounted on the syringe, the vials opened or perforated, and the plunger of the syringe retracted. Considerable risk of contamination of the medium exists when these measures are carried out.
Processes permitting simultaneous formation and charging of containers by blow moulding or vacuum moulding are already known. DE 197 07 292 A1, for example, discloses such a blow moulding process.